1. Technical Field
The present invention relates to a rubber stopper for a waterproof connector for the purpose of waterproofing electric wires which are equipped with terminal clamps at their ends, from an inlet side where the electric wires are inserted into the connector, and the waterproof connector employing this rubber stopper.
2. Background Art
Various electrical appliances are mounted on a vehicle body of an automobile. For the purpose of supplying electric power for actuating these electrical appliances, and sending control signals, there is arranged a wire harness including a number of electric wires bundled. A connector for connecting the electric wires to the electrical appliances is provided at an end of the wire harness. This connector generally includes terminal clamps formed of metal having favorable electrical conductivity, an insulating connector housing for containing a plurality of the terminal clamps connected to core wires of the electric wires, and so on. Moreover, the connector has a cylindrical shape or a box-like shape.
Recently, in view of diversification of customers' needs and in order to improve global environment, variety of the above described electrical appliances to be mounted has more and more increased, and accordingly, high reliability, lightweight, versatility, and compactness of the electrical appliances has been more keenly required. Particularly, there is a tendency to concentrate an ECU (Electronic Control Unit) in an engine room. In case where the ECU is concentrated in the engine room, it is a serious problem to secure heat resistance of various constituent elements of the electrical appliances, such as an IC, and to reliably secure waterproofing performance against rainwater, car wash, etc.
As a waterproof connector for securing the waterproofing performance of the above described problem, a waterproof connector employing a pair of rubber stoppers in a two split mold which are provided with arc-shaped fitting grooves for fitting the electric wires has been heretofore proposed. The waterproof connector of this type employing the rubber stoppers in the two split mold is disclosed in the following patent documents, for example.
[Patent Document 1] JP-A-10-284168
[Patent Document 2] JP-A-2000-323229
[Patent Document 3] JP-A-2006-302850
In the aforesaid Patent Document 1, there is proposed a waterproof connector including a connector body which contains a plurality of terminal clamps connected to electric wires and arranged in parallel, and a rubber plug which is fitted to a recessed part provided on a connection side of the electric wires. The rubber plug is provided with wire fitting grooves for respectively fitting half peripheral parts of the electric wires, on respective contact faces of a pair of split mold bodies which are formed in the two split mold. It is further disclosed that rubber plug pressing grooves are provided at an intermediate position between the two adjacent wire fitting grooves on the outer peripheral surface of the rubber plug, and pressing ribs adapted to be engaged with these rubber plug pressing grooves are provided on an inner face of the recessed part of the connector body. It is further described, in Patent Document 1, that when the rubber plug consisting of a pair of the split mold bodies having the electric wires inserted into the wire fitting grooves is fitted into the recessed part of the connector body, the pressing ribs are engaged with the rubber plug pressing grooves to further compress the rubber plug, whereby waterproofing performance of contact parts between the electric wires and the split mold bodies of the rubber plug is improved.
In the aforesaid Patent Document 2, there is proposed a rubber plug in a two split mold formed with electric wire insertion holes having a semicircular sectional shape into which electric wires equipped with terminal clamps are inserted. It is disclosed that this rubber plug in the two split mold is divided at a plane traversing the electric wire insertion holes, and coupled by a hinge so as to be opened and closed. For assembling this rubber plug, as a first step, the terminal clamps connected to the electric wires are inserted into cavities in a housing. Then, the electric wires are clamped by the electric wire insertion holes of the rubber plug in the two split mold, and thereafter, the rubber plug in a closed state is fitted into a common inlet of the housing.
In the aforesaid Patent Document 3, there is proposed a waterproof packing in a two split mold which is coupled by a hinge at one side and provided with electric wire insertion holes having a semicircular sectional shape on inner faces of the waterproof packing which form contact faces, wherein a thermoplastic adhesive is further adhered to the contact faces, the electric wire insertion holes and an outer peripheral faces of the waterproof packing. In the invention disclosed in Patent Document 3, the waterproof packing in the two split mold having the electric wires equipped with the terminal clamps inserted into the wire insertion holes is inserted into an outer housing of a waterproof connector, and heat is added to the thermoplastic adhesive from outside, whereby the thermoplastic adhesive which is adhered to the wire insertion holes is melted thereby to bond and fix outer peripheral faces of the electric wires to inner peripheral faces of the wire insertion holes.
At the same time, the thermoplastic adhesive adhered to the outer peripheral face of the waterproof packing is also melted thereby to bond and fix the outer peripheral face of the waterproof packing to an inner peripheral face of a packing container in the outer housing, whereby waterproofing performance between the electric wires and a mounting side of the connector housing is enhanced.
The rubber plug (or the waterproof packing) in the two split mold as is disclosed in the aforesaid Patent Documents 1 to 3 is equally divided in two, and so, the wire insertion holes for clamping the electric wires which are formed on the contact faces have a semicircular shape in cross section. This will be described referring to FIGS. 6A and 6B. Wire insertion holes 23a . . . 23b . . . which are formed between contact faces 22a, 22b of a pair of upper and lower rubber plugs (rubber stoppers) 21a, 21b have a semicircular or a substantially semicircular shape. Therefore, when the contact faces of a pair of the upper and lower rubber plugs 21a, 21b contact each other, after electric wires 24 having a circular sectional shape have been inserted into spaces in a cylindrical shape which are formed by the opposed wire insertion holes 23a and 23b, there has been such possibility that positional deviations 25 may occur on the contact faces 22a, 22b between the adjacent wire insertion holes 23a or 23b, as shown in FIG. 6B.
The reason why the positional deviations 25 occur on the contact faces 22a, 22b of the conventional rubber stoppers 21a, 21b in the two split mold is as follows. Operation for inserting the electric wires 24 into the wire insertion holes 23a . . . , 23b . . . which are formed on the contact faces 22a, 22b of the rubber stoppers 21a, 21b in the two split mold is conducted in the following manner.
As a first step, the electric wires 24 are inserted into the wire insertion holes 23b . . . of the rubber stopper 21b at a lower side, as shown in FIG. 6A, and thereafter, the rubber stopper 21a at an upper side is mated to the rubber stopper 21b at the lower side. Because the wire insertion holes 23a formed in the upper rubber stopper 21a have a semicircular or a substantially semicircular shape, an area where the semicircular-shaped parts come into contact with surfaces of the electric wires 24 is increased, when conducting this operation for mating the upper rubber stopper 21a to the lower rubber stopper 21b, after the electric wires 24 have been inserted into the wire insertion holes 23b of the lower rubber stopper 21b. Therefore, there has been such a risk that the positional deviations 25 may occur due to contact resistance between the wire insertion holes 23a and the surface of the electric wires 24. When such positional deviations 25 as shown in FIG. 6B have occurred, gaps are formed between the contact faces 22a, 22b of the rubber stoppers 21a, 21b in the two split mold, and waterproofing performance will be deteriorated.